One rotatingly driven plate can, at the same time, constitute the axially displaceable one, but this would be an exception. Normally, the supported plate is rotatingly driven and the axially displaceable plate which, in turn, is supported via the balls on the supported plate is held in a rotationally fast way.
For actuating the axial setting device, the driving motor is driven in a first direction of rotation. The at least one plate coupled to the driving motor via reduction stages of the driveline is rotated, and the displaceable plate, which, in turn, axially supports itself on the axially supported plate is axially displaced against elastic returning forces of the spring mechanism.
The balls which, in pairs of ball grooves, rest against end stops and which, at the same time, are positioned there in the deepest groove portions are caused, by the relative rotation of the plates relative to one another, to move towards flatter groove portions, as a result of which the plates push each other away from one another.
If the driving motor is driven in the opposite direction or de-energised, the elastic returning force of the spring mechanism acting on the displaceable plate causes the latter to be pushed back and the at least one rotatingly drivable plate is rotated backwards, either actively by the driving motor or due to the effect of the spring mechanism by way of the balls in the ball grooves until the balls in their pairs of ball grooves simultaneously abut the end stops. As a result of the balls abutting the ends of the ball grooves, the rotating masses of this system, i.e. the rotatable one of the plates, the gears of the driveline and the motor shaft of the driving motor with the rotor mass are stopped abruptly.
The elastic deformation of the motor shaft caused by stopping the rotating masses so abruptly can lead to tooth fracture at the pinion or at the gear set because the force impact points in the toothings move outwards due to the bending of the motor shaft, as a result of which the pinion or the gear set are subjected to loads which can exceed the design loads.